Apparatus for plasticizing a solid particulate material for extruding or molding



May 26, 1959 B T 2,887,719

APPARATUS FOR PLASTICIZING A SOLID 'PARTICULATE MATERIAL FOR EXTRUDING OR MOLDING Filed May 16, 1957 3 Sheets-Sheet 1 L I i3 INVENTOR HAROLD CoR BETT ATTORNEY May 26, 1959 H. CORBETT 2 APPARATUS FOR PLASTICIZING A SOLID PARTICULATE MATERIAL FOR EXTRUDING OR MOLDING Filed May 16, 1957 3 Sheets-Sheet 2 INVENTOR HAROLD CORBETT BY jgn'f w/ ATTORNEY May 26, 1959 HICORBETT 2,887,719

APPARATUS FOR PLA'STICIZING A SOLID PARTICULATE MATERIAL FOR EXTRUDING 0R MOLDING Filed May 16, 1957 I5 Sheets-Sheet 5 F|G'.4. I IQVENTOR HAROLD CORBETT BY #M ATTORNEY nited Stat patfit Harold Corlbett;Worcester,v Mass, assignor; by mesue assignments, to Package Machinery Company, East Iiongmeadow, Mass-. a corporation oflMa'ssa'chnsetts Application May. 16; 1957,'-'SerialNo. 660,025

7 Claims. 01. 1s-12 Thislinvention relates to an apparatusforplasticizing a solid particulate material; Plastic material discharged" by. the: device of Tth'is invention may be directly fed to' an extruder or; employed as a feeding mechanism for an injection molding operation.- This application is' a continua-tion inpart'of my copendingapplicationserial No. 58 33757, filed May'9, 1952, nowabandoned.

In most conventional plastic extruders' the raw plastic material is fed to a hopper in solid and particulate form: From the'hopper; the material is fed'to a treatingchamber where it is plasticized' by being-heated; mixedandcompressed. The:resulting melted orfused material is then forced outwardly (extruded) from'anlorificeat the terminallend of the heating-and mixing chamberi Convention ally,.in these extruders; the treatingchamlier is-hori zontallyidisposed with the vertical hopper being located near oneend of the chamber. Therefore; theplastic ma terial travelslinia vertical direction 'througlrthe' hopper and :in a horizontal direction through" the heating charm ber; Such convention'al extruders lack e-fli ciency in *p l'ast'i' cizing;the particulate material and are relativelycornplh catedg: bulky and space consuming:

In: molding many plastic" materials" the presence of moisture createsi: many problems and? if not thoroughly eliminatedaresults in the molded product heing'unaccept able fortuse or sale; Moistiire-= elimination-is" of" such" importance the? me or expensive and relatively comp1i= cated machin'esih'ave b'een emp'loyed'to separate moisture" and vapors from the plastiemraterial asitis-beingpre= pared for a moldin'g operationx- Othermoldetshave-predried their material. in' ov'ens -and' then protecte'd itfrom reabsorbing atmospheric moisture until the molding oper ation:canbe completed;

Gner'objectofithisfiinventiomis toprovide anirnproved' apparatus for: pia'stici'zing a solid particulate material 3 for arrrextruding ori melding: operation; which" apparatus is? relatively. simple in? construction; compact" and highly" efiicient in redueing particulate plastic material to' a' fused or moldable state.

The ab'ove' and otherfrelatedobiectsand fe'aturesof the invention, will b'e apparent fr'om areading'of' the renewing. description of th'e disclesure found inthe accompany.- ingwdrawing and the particular novelty thereof pointedout in'sth'e appendedclaims:

Iii-the drawings Fig. l isa view in-f'rontelevation ofanwxti'uding'mw chine embodying. the present invention;

Figi2 is an enlarged vertical sectional View? of: the plastieizing apparatus incorporated inthe"extrtulirrg''rna' chine shown-inFigi 1;

Fig.- 3isan enlarged sectional view" taken along'section' line 3 -3 of' Fig. 1' showing theclmping 'liigsfor? the plasticizing' barrel;

Fig. 4* is an'enlarged vie w 'in fr o'ntelevation ofthe feed" screw itself; minus the cap;

Fig. 6 is a plan view of the cap shown in Fig. 5; and

Fig.- 7 is a view of the cap taken on an elevation 45 degrees removed from the line 5--5 of Fig. 6.

Referring to the drawings in detail, in Fig. 1 the numeral 10 designates a base or housing in which is mounted a suitable drive mechanism (not shown). A vertical plasticizer 11 having a hopper 12 is mounted on the upper surface-of the housing 10. An elongated water trough 13, having an open top, is situatedto theright of the extruder orifice- 14. At the extreme righthand end of the water trough 13 a motor 15' drives a lower roller 16 (shown partly in dotted lines). An upper weighted roller 17 rests against roller 16 so as to bedriven by surface contact therewith. Circulating cooling. water is introduced tothe trough 13-by means of pipe" 18 and shut-0E valve'19: At the right-hand end ofthe trough, water is removed through water drains 20 and 21; water drain 20 also forms part of the supporting structure for theright-ha'nd' end of the trough.

Referring now to Fig. 2, the plasticizing apparatus 11 includes a hollow and rotatable vertical feed screw shaft 22' which is coupled at its'lower endto a drive shaft 23 by means of a pin 24. Screw 22 is .rotatably mounted within a cylindrical barrel 25-whose lower flanged .portion 26 rests upon acomplementary seating ring 27 attached to the housing 10. At the right-hand side of barrel 25, and'at a location spacedupwardly from the bottom there* of, is a discharge port which takes=the form of an out-' let pipe 28 integral with the barrel 25. The extruding orifice or die 14 is heldagainst the right-hand end of the ohtlet'28 by meansofa split clamp 29 and anadjustable holding strap (or heater band) 30. The latter strap 30 has a heater element-iimbedded therein for the-purpose of maintainingthe orifice member 14 at the required tern-'- perature; Additional heater bands'31 and 32 surround the barrel 25* at locations above and below outlet- 28, respectively. Another heater ba'nd33 also surrounds the outlet i pipe 28 between the barrel 25 and the heaterband-'30.

The-feed screw 22 (see Figs; 2 and 4) has upper co'n volutions 34 which may be referred to hereinafter as the screw flight 34'and it also has lower convolutions 35 of opposite hand which may bereferred to hereinafter as the reversescrew flight 35;. The flights 34, 35; although opposed, are formed with the same angle or pitch, this is'-- of importance in neutralizing the" thrust imparted to shaftZZwhen' it is rotated to discharge plastic through: the outlet pipe 28-thus minimizingthe loading onthe shaft bearing; Th6 tW0 SCl6WfilghtS34 and 35 are spaced apart along the screw'and barrelzat the disc-harge port' 28.-andcooperate with the-screw body and: barrel to define -a mixingchamber where theplastic material will be foldedlb'ack on itself and kneaded before being discharged th'rough the outlet pipe'28: This particular action has been found'highly. effective inreducing the plastic materialfto a substantially whole plastic or fused moldablestate in the relatively short distance illustrated. It Will alsobe notedthat preferably the" upper flight 34 terminates" ab'oveorcoeXtensively withtheu'pp'er end of the discharge port 2'8 whilethelowerflight'SFterminates below or co-' extensivelywith the lower end-of the discharge port-28. With ithis arrangernent the' fused plastic will be uniformly discharged without J anyi undesirable pulsating.

The: upper: end of feed screw 22 has: a. threaded hole 40w (Fig; 4') for receiving;thercomplementary threaded 7 portion 41- of'a head or cap. member 42='-(Fig.: 5;).1 An

enlarged cylindrical cavity; 43=extends within the: feedi screw fromlthe=lower end of' the threaded hole'40-to the bottom end.of.the. feediscrew. Thelower end oflthe cavity 43 is closed by. the drive-shaft 23.-

Referring nowto Figs.- 5; 6 and 7; the. cap member-. 42"'1ias'a'ho11ow'bullet shapedbodyportion 44and a lower reduced threaded portion 41, as referred to above. Four vertical agitator vanes 45, equally spaced from each other, project upwardly from the surface of the body portion 44. At the top of the cap a tapered threaded hole 46 is provided for receiving a correspondingly tapered plug, as will hereinafter appear. Below the threaded hole 46, an elongated cylindrical bore 47 extends from the hole 46 to the lower end of threaded portion 41. A series of small channels 48 extend substantially radially outward from bore 47 to the outer surface of the cap, forming rows of outlet ports 49 at positions between the vanes 45.

Returning now to Fig. 2 a tapered threaded plug 50 is adapted to screw into threaded hole 46 of the cap 42. An elongated hollow tube 51, passing through a hole in the plug 50 and welded to the same, extends from above the center of the hopper 12 through bore 47 and into the cavity 43 of the feed screw 22. The lower end of this hollow tube 51 terminates short of the drive shaft 23. A hollow swivel-type adaptor 52 (see Fig. l) is attached to the upper end of the tube 51 to permit easy connection to a source of air pressure (not shown).

The upper portion of barrel 25 is provided with a circumferential flange 53 substantially equal in size to lower flange 26. A relatively thin casing 54, provided with suitable holes for any projecting parts, fits around upper and lower flanges 53 and 26, respectively, so as to form an annular space with the outside of the barrel 25.

The feed hopper 12 is composed of inner and outer hopper members 55 and 56, respectively, between which is an upwardly tapering annular space. Outer hopper member 56 is attached at its lower end to an annular ring 57 which seats on the annular flange 53. These two annular members are held together by suitable screw means, not shown. The inner hopper 55 has a lower cylindrically shaped portion 58 whose inner diameter is substantially equal to the outer pitch diameter of the screw flight 34. The lower edge of this cylindrical portion 58 fits within the annular ring 57 and against the upper surface of annular flange 53. Inner hopper 55 has an upper curled edge 59 which fits over the upper edge of outer hopper 56 to close the latter. The upper edges of the two hopper members may be fastened together by screws, if desired.

Correspondingly situated holes 60 and 61 are provided in the ring 57 and the flange 53, respectively, at various locations around the circumference of the latter members for permitting communication between the upper and lower annular spaces. A plurality of circumferentially spaced holes 62 are formed in the outer hopper member 56 at a position below the upper edge thereof.

' As shown in Fig. 1, and as best illustrated in Fig. 3, clamping means are provided to hold the barrel 25 against the base member 10. This clamping means consists of a pivotal clamping lever 63 having a substantially horizontal end portion 64 adapted to fit over the edge of annular flange 26, and an upwardly inclined handle portion 65. Turning the clamping lever 63 to the position shown in Fig. 3 will force the annular flange 26 of the barrel 25 firmly against the annular ring 27 of the base member 10. A suitable slot 66 is provided in the barrel casing 54 to permit the lever to be turned in or out of engagement with the flange 26. Although but one clamping means has been illustrated in the drawings, it should be understood that there are actually two such members, with one being located on either side of the barrel. Each lever 63 is mounted on a cylindrical supporting member 67 which is welded to the base 10. Each of these levers 63 is held against its support 67, for free pivotal move ment thereon, by means of a bolt 68 and a nut 69, as shown. Fixed handles 70 (shown only in end view in Fig. 1) screwed into the flange 53 at opposite sides of the barrel may be used to assist in the lifting of the barrel assembly, including casing and hoppers, after the clamping means 63 have been released.

At the left-hand side of Fig. 1 is shown a panel board 71 having various controls thereon for regulating the speed of the drive shaft 23, the speed of the motor 15, and the amounts of heat dissipated by the various heater elements 30, 31, 32 and 33. These control means are well known items of standard merchandise and form no part of this invention.

A better understanding of the above described invention should be obtained from a description of its operation, as follows: Plastic material, in solid pellet or powdered form, is loaded into the hopper 12 (or, more specifically, into the inner hopper 55). The feed screw 22 is caused to rotate after the heaters have been brought to their required temperatures. The plastic material will be forced downwardly by the upper screw flight 34 into the lower portion of the barrel. At the same time, reverse fiight 35 will force plastic material upwardly from the bottom of the barrel and fold it back on further descending material in the space opposite outlet 28 creating a compression zone as well as a kneading action. Furthermore the opposite forces of the two screw flights tend to equalize the axial thrust on the screw 22 which means that the drive mechanism (not shown) can be simplified accordingly.

As a result of the compression and heating of the plastic material, the latter has become plasticized or molten in the zone opposite the outlet 28. Also, since this material is under compression, it will be extruded from the orifice opening of the orifice member 14 into the bath 13. The resulting rod or strip of extruded plastic material can be directed along the length of water bath 13 into the bite of rollers 16 and 17. Suitably weighted immersion rollers (not shown) located adjacent the opposite ends of the water bath may be employed to hold the extruded material under the surface of the water. The speed of roller 16, as determined by the appropriate control setting for motor 15, can be adjusted in accordance with the rate of extrusion to pull the material through the water bath. In some instances, the speed of roller 16 may be regulated to control the ultimate thickness of the extruded product. The speed of feed screw 22 and the settings for the various heaters may be varied in accordance with the physical characteristics of the plastic material being extruded. During the feeding process, air passing through openngs, such as slots 66 (Fig. 1) or openings 75 (Fig. 2), into the annular space between the casing 54 and the barrel 25 will become heated. This hot air will rise upwardly through holes 61 and 60 into the space between the two hopper members, so as to warm the outer surface of the lnnerhopper 55. The net effect of this passage of hot 3.11 be evidenced by a pre-heating or drying of the material in the hopper. The hot air is permitted to escape through holes 62 in the outer hopper 56.

If additional pre-heating of the plastic material is reqmred or desired, a source of air pressure may be applied to the hollow tube 51 through the swivel connection 52. Air will pass downwardly through the center of the hollow tube 51 into the lower portion of the cavity 43. This air, absorbing heat from the feed screw 22, will pass upwardly in the cavity 43 (on the outside of tube 51) through the bore 47 of the cap 42, through the channels 48, and out of the ports 49 into the body of the plastic material in the hopper. This stream of hot air will preheat or dry the plastic material by direct contact. The rate of air flow through the ports 49 can be varied by regulating the pressure of the air supplied to the tube 51.

With the arrangement shown in the drawings, it may be observed that the feed screw (including screw flight 35 and agitator vanes 45) projects upwardly into the hopper. As a result of this relationship, the feeding actually commences in the hopper itself. In addition, agitator vanes 45 constantly stir up the material to prevent any agglomeration or clogging within the hopper as well as facilitating'thedryingoperatiorr:

Also, the vertical arrangement of this extruder permits a simple separation of the-barrelmember from its associatedfeed screw by rneans of' clamping lugs'63; such a featurewould be otherwise impossible in the conventional horizontal type of extruder. After the lugs 63 have been turned to"their releasing"positions; the entire barrel assembly, includingih'elioppers andibarrelcasing', may be lifted up; to expose" the; feed screw" for inspection or cleaning:

The"embodiment"of;tliis'"invention, as set'forthin the drawings; has been-describediin particular reference'to an extruding system; As indicated above; the device of this invention couldbe adaptedforuse in connection with a plastic'm'olding'machine, in which'instance' this device would form the feedingmechanism for such a machine.

Also, this'invention'has beenidescribed in relation to the extrusion and molding of materials commonly referred to as plastic'material.' ltshould beiapparent, however, that the"device: ofthis 'invention' couldlbe employed in connection with other "fusible" materials," such as finelydivided glass, various-rubbercompounds, lead; tin, zinc and many other materials .whichanelt or may be plasticized at relatively low temperatures.

It will be obvious that other changes and modifications, apartzfrom-ithose described or suggestedlherein, may be made within the scope and spirit of thisrinventione There fore; it is intended that the above+description ofthe: instant invention, should be interpreted-in" an illustrative rather than -a limiting sense.

Having, thus described my, inventionuwhat I claim" as novel and desire to,securebyLetters,Patent of the United States is:

1; Apparatusforplasticizinga solidparticulate material for purposes of extruding or molding the same and com prising in combination, a substantially vertical barrel, a hopper connected with the barrel to introduce the material thereto, means for heating the barrel to fuse the material therein, a hollow rotatable screw disposed in the bore of the barrel and having upper convolutions arranged to feed the material downwardly when the screw is rotated in one direction and also having lower convolutions of opposite hand, the said upper and lower opposite hand convolutions terminating at points spaced from each other along the screw and barrel and defining therewith a mixing chamber wherein the material is kneaded and folded upon itself, means defining a discharge passage in the barrel communicating with said mixing chamber, a head supported on the upper end of the said screw, and a tube supported by said head extending from said hopper into the interior of the hollow screw, the said tube being adapted for connection with a source of air under pressure to introduce pressurized air to the interior of the screw for warming therein, and the said head being provided with passage means for the circulation of the warmed air from the interior of the screw to the particulate material in the hopper whereby moisture is removed from the said material.

2. Apparatus for plasticizing a solid particulate material for purposes of extruding or molding the same and comprising in combination, a substantially vertical barrel, a hopper connected with the barrel to introduce the material thereto, means for heating the barrel to fuse the material therein, a hollow rotatable screw disposed in the bore of the barrel and having upper convolutions arranged to feed the material downwardly when the screw is rotated in one direction and also having lower convolutions of opposite hand, the said upper and lower opposite hand convolutions terminating at points spaced from each other along the screw and barrel and defining therewith a mixing chamber wherein the material is kneaded and folded upon itself, means defining a discharge passage in the barrel communicating with said mixing chamber, a head supported on the upper end of said screw within the hopper having a plurality of vanes for agitating the material' in" the hopper during rotation of the screw, anda tube supported' by said head and projecting from said hopper-intothe interior of the hollowscrew, the said'tub'e being=adaptedfor connection' with a source of air under pressure to-submit'air to the hollow screw for warming, and the said headbeing provided with a plurality of passagesforthe flow of warmed air from the interior ofthe screwto"the'particulatematerial in the hopper so as'to removemoisture therefrom;

3; Apparatus forplasticizing a solid particulate mate-- rial forpurposesof extruding or molding the same and barrel-and having upper convolutions arranged to feed the material downwardly when the screw is rotated in "one direction-andalso having lower convolutions of oppositehand, the'saidupperand'lower opposite hand convolutions terminating at points spaced from each other along the'screwand barrel and defining therewith a mixing. chamherwherein the material iskneaded' and folded upon itself, means-defi'ninga discharge passage inthe' barrel communicating with'said mixing chamber, and a casing,

surroundingsaid barrel and said hopper which is closed at the bottom and closed at thetop'but which is provided witha"pluralityofopenings adjacent its bottom endand top end'for the' circulati'on of air therethrough, the said' air beingheated'by'thebarrel so asto heat the hopper and t pre-heat the-particulate material therein.-

4; Apparatus for plasticizing a solid particulate mate rial forpurposes of extruding or 'molding thesame and comprising incombination; a' substantially vertical barrel," a hopper connectedwiththe barrel to introducethe material thereto, means for heating the barrel to fuse the material therein, a hollow rotatable screw disposed in the bore of the barrel and having upper convolutions arranged to feed the material downwardly when the screw is rotated in one direction and also having lower convolutions of opposite hand, the said upper and lower opposite hand convolutions terminating at points spaced from each other along the screw and barrel and defining therewith a mixing chamber wherein the material is kneaded and folded upon itself, means defining a discharge passage in the barrel communicating with said mixing chamber, a head supported on the upper end of the said screw, a tube supported by said head extending from said hopper into the interior of the hollow screw, the said tube being adapted for connection with a source of air under pressure to introduce pressurized air to the interior of the screw for warming therein, and the said head being provided with passage means for the circulation to the warmed air from the interior of the screw to the particulate material in the hopper whereby moisture is removed from the said material, and a casing surrounding said barrel and said hopper which is closed at the bottom and closed at the top but which is provided with a plurality of openings adjacent its bottom end and top end for the circulation of air therethrough, the said air being heated by the barrel so as to heat the hopper and preheat the particulate material therein 5. Apparatus for plasticizing a solid particulate mate rial for purposes of extruding or molding the same and comprising in combination, a substantially vertical barrel, a hopper connected with the barrel to introduce the material thereto, means for heating the barrel to fuse the material therein, a hollow rotatable screw disposed in the bore of the barrel and having upper convolutions arranged to feed the material downwardly when the screw is rotated in one direction and also having lower convolutions of opposite hand, the said upper and lower opposite hand convolutions terminating at points spaced from each other along the screw and barrel and defining therewith a mixing chamber wherein the material is kneaded and folded upon itself, means defining a discharge passage in the barrel communicating with said mixing chamber, a head supported on the upper end of said screw within the hopper having a plurality of vanes for agitating the material in the hopper during rotation of the screw, a tube supported by said head and projecting from said hopper into the interior of the hollow screw, the said tube being adapted for connection with a source of air under pressure to submit air to the hollow screw for warming, and the said head being provided with a plurality of passages for the flow of warmed air from the interior of the screw to the particulate material in the hopper so as to remove moisture therefrom, and a casing surrounding said barrel and said hopper which is closed at the bottom and closed at the top but which is provided with a plurality of openings adjacent its bottom end and top end for the circulation of air therethrough, the said air being heated by the barrel so as to heat the hopper and preheat the particulate material therein.

6. Apparatus for plasticizing a solid particulate material for purposes of extruding or molding the same and comprising in combination, a barrel, a hopper connected with the barrel to introduce the material thereto, means for heating the barrel to fuse the material therein, a hollow rotatable screw disposed in the bore of the barrel and having convolutions arranged to feed the material in the barrel when the screw is rotated, means defining a discharge passage in the barrel to receive the material fed by the screw, 21 head supported on the end of the screw and projecting into said hopper, and a tube supported by said head extending from said hopper into the interior of the hollow screw, the said tube being adapted for connection with a source of air under pressure to introduce pressurized air to the interior of the screw for warming therein, and the said head being provided with passage means for the circulation of the warmed air from the interior of the screw to the particulate material in the hopper whereby moisture is removed from the said material.

7. Apparatus for plasticizing a solid particulate material for purposes of extruding or molding the same and comprising in combination, a substantially vertical barrel, a hopper connected with the barrel to introduce the material thereto, means for heating the barrel to fuse the material therein, a rotatable screw disposed in the bore of the barrel and having convolutions arranged to feed the material downwardly when the screw is rotated, means defining a discharge passage in the barrel to receive the material fed by the screw, and a casing surrounding said barrel and said hopper which is closed at the bottom and closed at the top but which is provided with a plurality of openings adjacent its bottom end and adjacent its top end for the circulation of air therethrough, the said air being heated by the barrel so as to heat the hopper and pre-heat the particulate material therein.

References Cited in the file of this patent UNITED STATES PATENTS 2,011,055 Klugh Aug. 13, 1935 2,499,398 Lyon Mar. 7, 1950 2,509,014 Payne et al.- May 23, 1950 2,653,348 Elgin et al Sept. 29, 1953 2,686,335 Gross Aug. 17, 1954 2,766,534 Schaub et al Oct. 16, 1956 FOREIGN PATENTS 930,773 France Aug. 25, 1947 

